The odors of an unfamiliar receptive female will evoke sexual motivation in the male common marmoset characterized by non contact penile erection. This odor-induced, psychogenic behavior provides a unique opportunity to study brain activity associated with sexual motivation in a nonhuman primate. With the advent of functional magnetic resonance imaging (fMRI) it is now possible to use a noninvasive approach for observing brain activity without injury or sacrifice of the animal. Recently, a small animal holding device was developed for performing fMRI on a fully awake male marmoset, acclimated to the imaging procedure. During MR imaging, a male marmoset can be sexually motivated by the odors of an unfamiliar receptive female without any other visual, auditory or somatosensory stimulation. These studies will use fMRI to examine the temporal activation and neuropharmacology of the neural networks involved in sexual motivation in the marmoset. It is hypothesized that smelling odors of an unfamiliar receptive female will increase neural activity in brain areas involved in sexual motivation. To test this hypothesis, changes in brain activity in male marmosets will be visualized with fMRI during exposure to odors of receptive females. During brain imaging, animals will be treated with dopamine receptor agonists and antagonists to examine the central effects of drug intervention on sexual motivation and endocrine responses. Using fMRI on conscious marmosets, it will be possible to study the neurobiology of affiliation, fear, and aggression triggered by relevant sensory cues and how experience can alter brain activity. Indeed, the long-term goal of this research is to understand the neurobiology contributing to sexual violence. Throughout the animal kingdom there are many examples of heightened male sexual motivation rapidly reverting to intense aggression, oftentimes violent, lethal behavior during competition for a receptive female. We hypothesize that sexual and aggressive motivations share a common neurobiology that contribute to the escalation and expression of sexually violent behavior. These studies are the first step in identifying that common neurobiology in a non human primate. There are no effective psychosocial intervention strategies or drug treatments to help violent sex offenders. This is an extremely important area of mental health that impacts on public safety and criminal corrections.